Apparatus for cleaning exhaust gases

ABSTRACT

An apparatus for cleaning an exhaust gas comprising an elongated housing capable of receiving a catalyst monolith, said housing provided at one end with an exhaust gas entry opening, and provided at the other end with an exhaust gas discharge opening, at least two bridges spaced apart within said housing and attached to said housing, at least one supporting rod for said monolith, said rod secured to one of said bridges and movably mounted on another of said bridges, a monolith catalyst having flow channels and at least one bore for receiving said at least one supporting rod, said bore being provided in the direction of said flow channels, and an elastic intermediate layer surrounding said at least one supporting rod, said catalyst held on said rods by said layer being under pressure. The apparatus is especially useful for cleaning exhaust gases from internal combustion engines.

United States Patent [1 1 Birtigh et a1.

[ Dec. 16, 1975 APPARATUS FOR CLEANING EXHAUST GASES [75] Inventors:Gerhard Birtigh, Frankfurt; Horst Parbel, Gelnhausen; Heinrich Sauer,Grossauheim, all of Germany [22] Filed: Mar. 12, 1974 [21] Appl. No.1450,518

[30] Foreign Application Priority Data Mar. 16, 1974 Germany 2313156[52] US. Cl. 23/288 FC [51] Int. Cl. 1301.] 8/02; B01J 35/04; FOlN 3/15[58] Field of Search 23/288 FC,288 F [56] References Cited UNITED STATESPATENTS 1,932,927 10/1933 Fischer 23/288 FC UX 3,124,930 3/1964 Powers23/288 FC UX 3,211,534 10/1965 Ridgway 23/288 FC UX 3,248,188 4/1966Chute 23/288 FC UX 3,362,783 1/1968 Leak 23/288 FC X 3,492,098 l/l970DePalma et a1 23/288 FC UX 3,558,286 1/1971 Gourdine 23/288 F 3,692,4979/1972 Keith et a1. 23/288 FC 3,773,894 11/1973 Bernstein et al 23/288FC UX 3,798,006 3/1974 Balluff 23/288 FC Primary Examiner-Morris O. WolkAssistant Examiner-Michael S. Marcus Attorney, Agent, or Firm-Browne,Beveridge, DeGrandi & Kline 57 ABSTRACT An apparatus for cleaning anexhaust gas comprising an elongated housing capable: of receiving acatalyst monolith, said housing provided at one end with an exhaust gasentry opening, and provided at the other end with an exhaust gasdischarge opening, at least two bridges spaced apart within said housingand attached to said housing, at least one supporting rod for saidmonolith, said rod secured to one of said bridges and movably mounted onanother of said bridges, a monolith catalyst having flow channels and atleast one bore for receiving said at least one supporting rod, said borebeing provided in the direction of said flow channels, andvari elasticintermediate layer surrounding said at least" one supporting rod, saidcatalyst held on said rods by said layer being under pressure. Theapparatus is especially useful for cleaning exhaust gases from internalcombustion engines.

U.S. Patent Dec. 16, 1975 3,926,565

I um I:

FIG. 1

FIG. 2 FIG. 3

6 1 CAPILLARY 2 DIAMETER .FIG.5

FIG.6

APPARATUS FOR CLEANING EXHAUST GASES This invention relates to anapparatus for cleaning exhaust gases,-such as exhaust gases from aninternal combustion engine.

When the apparatus includes a monolithmade of 1 ceramic material, itmust be anchored in the metal housing. Constructions have been known inwhich the monolith is puttied in with cement. One disadvantage of thismethod of construction is that the cement is under aheavy load and canbreak as a result of mechanical shock or as a result of the combustiongases emerging from theengine cylinders in a sequence of high impluses.To these causes of failure must'be added the differing thermal expansionproperties of the ceramic and metal. In the case of high temperatures,the metal housing can be lifted from the rigidly puttied ceramic corebecause of the differing thermal expansion properties.

In other known methods of construction, the monolith is forced intoposition by an elastic mass between the housing and body. This mass mustbe kept under a pressure sufficiently high to hold the monolith firmlyin place, despite the considerably greater thermal expansion propertiesof the metal housing at high temperatures. With prolonged operatingtimes, the steel jacket of the housing can expand to such an extent,that the prestressed ceramic monolith weakens. This results in themonolith no longer being firmly anchored in the housing.

Accordingly, there exists a need in the art for an apparatus forcleaning exhaust gases which will aid in overcoming the previousproblems. The apparatus should be capable of withstanding mechanicalshock and the sequence of high impluses of combustion gases which emergefrom the cylinders of an internal combustion engine. Furthermore, theapparatus should be less susceptible to failure because of the differentthermal expansion properties of the ceramic material comprising thecatalyst and the metallic housing which holds the catalyst.

This invention aids in overcoming the disadvantages associated withprior art devices by providing an apparatus for cleaning an exhaust gasin which the apparatus comprises an elongated housing capable ofreceiving a catalyst monolith, and further in which the housing isprovided at one end thereof with an exhaust gas entry opening and at theother end thereof with an exhaust gas discharge opening. At least twobridge means are spaced apart from each other within the housing, andeach is attached to the housing. There is also provided at least onesupporting rod for the monolith. The sup porting rod is secured to oneof the bridge means and shiftably mounted on another of the bridgemeans. The apparatus includes a monolith catalyst positioned in theelongated housing. The monolith catalyst has flow 2 channels and atleast one bore for receiving the supporting rod. The bore is provided ina direction substantially parallel to the direction of flow of gasesthrough the flow channels. An elastic, intermediate layer surroundingeach supporting rod is also provided. The catalyst is held inposition onthe supporting rod by the layer being under pressure. Preferably, onebridge means is positioned near the gas entry opening and another of thebridge means is positioned near the gas discharge opening, and one endof at least one rod is attached to the bridge means near the gas entryopening while the other end of the rod is shiftably mounted on thebridge means near the gas discharge opening.

In a further embodiment, a space exists between the housing andthe-monolith, and sealing means are provided in this space.Preferably,the sealing means comprises a gasket or a labyrinth packing.In a preferred embodiment, the space between the housing and themonolith is less than about one-half of the diameter of a flow channelin the monolith.

The elastic, intermediate layer between the supporting rod and themonolith is advantageous because it effectively dampens the sequence ofshocks caused by the pulses of exhaust gases emanating from the engine.

The intermediate layer can consist of any kind of temperature resistant,resilient material. Preferably, the elastic, intermediate layer is a webof wire, rock wool, asbestos wool, spun glass or silica-alumina (e.g.fiberfrax). The housing can be provided with a heat insulating jacket orwith cooling ribs or cooling vanes. Generally, the cooling ribs or vaneswill be on the outside of the housing.

This invention will be explained in greaterdetail with reference to thedrawing in which:

FIG. 1 is a cross-section of an exhaust gas cleaning apparatus accordingto this invention, and l I FIGS. 2, 3 and 4 depict preferred embodimentsinvolving thespace between the housing and the catalyst monolith.

FIG. 5 depicts a housing having a circular cross-section taken along 5-5 of FIG. 1

FIG. 6 depicts an embodiment alternative to FIG. 5.

The holding arrangement depicted in FIG. 1 avoids the disadvantages ofknown exhaust gas cleaning de vices, while retaining the advantagesassociated with an elastic, intermediate layer between metal parts and amonolith ceramic. Referring to FIG. 1, a monolith l is held in positionby a metal rod 2. Between the monolith 1 and rod 2 is an elastic mass 3(e.g. fiberfrax fibers) under pressure. Elastic mass 3 is held inposition by the frictional forces on the metal rod and on the monolith.The metal rod 2 is securely attached to housing 6, which is ofsubstantially cylindrical shape, by means of bridges 4 and 5. Housing 6is provided with an exhaust gas inlet opening 7 and an exhaust gasdischarge opening 8. The rod 2 is fixedly secured to bridge 4. It isshiftably mounted in bridge 5. The pressure thrust of the exhaust gasesare absorbed by not only the elastic, intermediate layer 3, but also bythe elasticity of the metal rod 2 and flexibility of the bridge. Sincethe ceramic monolith exhibits only slight thermal expansion, the contactpressure between the rod and monolith does not decrease even in the caseof high operating temperatures. Furthermore, loosening of the connectionbetween metal and ceramic which occurs in prior art devices, cannotoccur in the device of this invention.

Since the metal housing 6 does not perform any holding functions, thecross-section thereof can be arbitrarily selected. For example, in FIG.5, a housing having a substantially round cross-section is shown. Whenhousings having round crosssections are employed, a single supportingrod is generally sufficient. In FIG. 6, a housing 6 having an elongatedcross-section is depicted, and two supporting rods 2 are shown. In theforegoing Figs, like numerals have like meanings.

The sealing means between the housing 6 and the monolith 1 can be freelyselected. A labyrinth, such as that depicted in FIG. 2, as well as agasket, such as that depicted in FIG. 3, can be employed. The sealingmeans can be continuous or discontinuous (i.e. having openings thereinfor the passage of gases). The arrangement for holding the sealing meansin position will be apparent to persons skilled in the art.

It is particularly advantageous to fit the monolith in the housing withlittle clearance between these two elements since the entire catalystvolume can be effectively utilized. An adequate seal can be achievedwhen the distance between the catalyst and housing is less than aboutone-half the diameter of the flow channels in the monolith. This isdepicted in FIG. 4.

The outside surface of the monolith can still serve as an effectivecatalytic surface. During operation, good heat transmission can beprovided in order to avoid overheating of the catalyst. In the presentinvention, in which the monolith is positioned in the metal housingwithout insulation, a large portion of the reaction heat can betransmittedthrough the wall of the housing. Cooling effects can beenhanced by providing cooling vanes or ribs on the housing.

This invention has several advantageous features. First of all, theadverse effects of mechanical shock are minimized because of the methodof construction of the apparatus of this invention. Furthermore, thesequence of rapid impulses of exhaust gases from an internal combustionengine can be absorbed by the device of this invention without damage tothe monolith or apparatus. Additionally, since the ceramic monolith isnot in direct contact with a metallic surface, the differences inthermal expansion properties for the ceramics and metals is nottroublesome.

What is claimed is:

1. An apparatus for cleaning an exhaust gas comprising an elongatedmetal housing capable of receiving a catalyst ceramic monolith, saidhousing provided at one end with an exhaust gas entry opening, andprovided at the other end with an exhaust gas discharge opening, atleast two bridge means spaced apart within said housing and attached tosaid housing, at least one supporting rod for said monolith, said rodsecured to one of said bridge means and movably mounted on another ofsaid bridge means, a ceramic monolith catalyst element having flowchannels for conveying the exhaust gas from the entry opening to thedischarge opening and at least one bore for receiving said at least onesupport rod and the largest cross-sectional dimension of said ceramicbeing smaller than the adjacent respective internal cross-sectionaldimension of said housing to form a space therebetween, said bore beingprovided in the direction of said flow channels, and an elastic,intermediate layer surrounding said at least one supporting rod and heldthereon by said layer being under pressure.

2. An apparatus according to claim 1 in which one of said bridge meansis positioned near said gas entry opening and one of said bridge meansis positioned near said gas discharge opening.

3. An apparatus according to claim 1 in which said elastic, intermediatelayer is a web of wire, spun glass, alumina-silica fibers, rock wool orasbestos wool.

4. An apparatus according to claim 1 in which sealing means are providedin said space between said housing and said monolith.

5. An apparatus according to claim 4 in which said sealing meanscomprises a gasket or a labyrinth.

6. An apparatus according to claim 4 in which the flow channels of themonolith are of substantially equal diameter and said space is less thanabout one-half of the diameter of a flow channel.

7. An apparatus according to claim 1 in which one of said bridge meansis positioned near said gas entry opening and another of said bridgemeans is positioned near said gas discharge opening, and one end of atleast one of said rods is attached to the bridge means near said gasentry opening and the other end of said rod is movably mounted on thebridge means near said gas discharge opening.

8. apparatus according to claim 7 in which sealing means comprising agasket or a labyrinth are provided in said space.

9. An apparatus according to claim 8 in which said elastic, intermediatelayer is a web of wire, rock wool,

asbestos wool, spun glass or alumina-silica fibers.

1. AN APPARATUS FOR CLEANING AND EXHAUST GAS COMPRISING AN ELONGATEDMETAL HOUSING CAPABLE OF RECEIVING A CATALYST CERAMIC MONOLITH, SAIDHOUSING PROVIDED AT ONE END WITH AN EXHAUST GAS ENTRY OPENING, ANDPROVIDED AT THE OTHER END WITH AN EXHAUST GAS DISCHARGE OPENING, ATLEAST TWO BRIDGE MEANS SPACED APART WITHIN SAID HOUSING AND ATTACHED TOSAID HOUSING, AT LEAST ONE SUPPORTING ROD FOR SAID NONOLITH, SAID RODSECURED TO ONE OF SAID BRIDGE MEANS AND MOVABLY MOUNTED ON ANOTHER OFSAID BRIDGE MEANS, A CERAMIC MONOLITH CATALYST ELEMENT HAVING FLOWCHANNELS FOR CONVEYING THE EXHAUST GAS FROM THE ENTRY OPENING TO THEDISCHARGE OPENING AND AT LEAST ONE BORE FOR RECEIVING SAID AT LEAST ONESUPPORT ROD AND THE LARGEST CROSS-SECTIONAL DIMENSION OF SAID CERAMICBEING SMALLER THAN THE ADJACENT RESPECTIVE INTERNAL CROSS SECTIONALDIMENSION OF SAID HOUSING TO FORM A SPACE THEREBETWEEN, SAID BORE BEINGPROVIDED IN THE DIRECTION OF SAID FLOW CHANNELS, AND AN ELASTIC,INTERMEDIATE LAYER SURROUNDING SAID AT LEAST ONE SUPPORTING ROD AND HELDTHEREON BY SAID LAYER BEING UNDER PRESSURE.
 2. An apparatus according toclaim 1 in which one of said bridge means is positioned near said gasentry opening and one of said bridge means is positioned near said gasdischarge opening.
 3. An apparatus according to claim 1 in which saidelastic, intermediate layer is a web of wire, spun glass, alumina-silicafibers, rock wool or asbestos wool.
 4. An apparatus according to claim 1in which sealing means are provided in said space between said housingand said monolith.
 5. An apparatus according to claim 4 in which saidsealing means comprises a gasket or a labyrinth.
 6. An apparatusaccording to claim 4 in which the flow channels of the monolith are ofsubstantially equal diameter and said space is less than about one-halfof the diameter of a flow channel.
 7. An apparatus according to claim 1in which one of said bridge means is positioned near said gas entryopening and another of said bridge means is positioned near said gasdischarge opening, and one end of at least one of said rods is attachedto the bridge means near said gas entry opening and the other end ofsaid rod is movably mounted on the bridge means near said gas dischargeopening.
 8. An apparatus according to claim 7 in which sealing meanscomprising a gasket or a labyrinth are provided in said space.
 9. Anapparatus according to claim 8 in which said elastic, intermediate layeris a web of wire, rock wool, asbestos wool, spun glass or alumina-silicafibers.